Vehicles including hybrid vehicles, electric vehicles and fuel-cell vehicles include a power storage device for storing electric power and an electric motor. As the electric power is supplied from the power storage device to the electric motor, the electric motor generates driving force for driving the vehicle. At the time of braking, the electric motor regenerates power. The regenerated electric power is supplied to the power storage device. Therefore, while the vehicle is running, charging and discharging of the power storage device are controlled such that an index value (SOC) indicating the state of charge of the power storage device is within an appropriate range. SOC is defined as a ratio of the current amount of charges with respect to the amount of charges in a fully charged state. SOC of the power storage device in the fully charged state is 100(%) and SOC of the power storage device not charged at all is 0(%).
By way of example, Japanese Patent Laying-Open No. 2004-56867 (PTL 1) discloses a hybrid vehicle control system in which control width of SOC of the power storage device is adjustable in accordance with traveling sections. The control system includes a road information acquiring unit acquiring road information of a scheduled travel route of the vehicle, a control width and traveling method determining unit for changing control width of SOC of power storage means and for determining the method of traveling of the vehicle, and a control processing unit for controlling traveling of the vehicle in accordance with the determined method of travel. The control width and traveling method determining unit calculates SOC of the power storage means (battery) in a prescribed section of the scheduled travel route of the vehicle, and based on the SOC, changes the control width of SOC. Further, the control width and traveling method determining unit determines the method of traveling of the hybrid vehicle such that SOC at the end of prescribed section is within the control width.
By way of example, Japanese Patent Laying-Open No. 2005-65352 (PTL 2) discloses a controller for controlling charging/discharging of a battery. The controller changes control width of battery SOC to prevent over-discharge of the battery, and avoids the influence of memory effect on charging/discharging of the battery. More specifically, the controller increases both the upper and lower limits of control width of the SOC, if memory effect occurs.